A highly selective fluorescent sensor for fluoride anion based on pyrazole derivative: Naked eye no-yes detection

Abstract A new pyrazole-based fluorescent sensor, 5-amino-3-(5-phenyl-1H-pyrrol-2-yl)-1H-pyrazole-4-carboxamide (compound 1 ), was studied for fluoride anion (F − ) detection in organic or water-containing solution. This compound displayed both changes in UV–vis absorption and fluorescence emission spectra upon addition of F − . With increasing of F − , blue emission intensity increases drastically and reaches saturation with 607-fold enhancement at 424 nm. The results indicate that compound 1 has highly selectivity for fluoride detection over other anions, such as Cl − , Br − , I − , HSO 4 − , H 2 PO 4 − and AcO − in DMSO or aqueous DMSO solutions. 1 H NMR titration and other experiments confirm that the sensing process is mainly from the deprotonation of the pyrazole–NH in compound 1 .